1. Field of the Invention
The present invention relates to radiant energy detectors; and more particularly, to a multispectral superconductive quantum detector array, individual superconductive quantum detectors for an array, and related methods.
2. Description of Related Art
Basically there are two general types of radiant energy detectors; namely, thermal detectors and quantum detectors. A thermal detector, which is sometimes referred to as a bolometer is in effect a very sensitive thermometer whose electrical resistance, for example, varies with temperature; and which is used in the detection and measurement of absorbed thermal radiation. A quantum detector changes its electronic characteristics without significant lattice heating in accordance with the radiant flux absorbed by the detector.
Photon sensors have significant applications in both commercial and military areas. For example, in commercial areas, photon sensors may be used for imaging, energy conservation by identifying thermal profiles of energy escape paths, mapping of agricultural and mineral resources from spectral signatures obtained from satellite images, identification of pollution emitted from industrial processes, detection of tumors in humans and defects in manufactured products from their temperature profiles, detection and measurement of the energy of ionizing radiation for medical applications, and nuclear non-proliferation treaty monitoring. Also, photon sensors may be used for night surveillance, reconnaissance, target identification, and guidance for missiles. However, the various individual applications for photon sensors involve different spectral bands, which are determined by performance advantages dictated by each particular application. Because of their broad spectral response, it is proposed to use an array of superconductive quantum detectors as a photosensor.
The feasibility of using an array of superconductive quantum detectors is determined by the size of the array; i.e., the number of individual superconductive quantum detectors, hereinafter referred to at times as (SQD), required for a particular application, the complexity of the array, and the difficulty and cost of manufacture.
Such an array is limited by the operational parameters of the individual SQD's and their associated read-out devices. A superconductive quantum interference device, referred to as SQUID can be used to read-out a SQD. For example, one of the important parameters that determines the magnitude and signal-to-noise ratio is the change in kinetic inductance developed in the detector loop by the radiant energy exposure. Another important operational parameter that determines the magnitude of the signal-to-noise ratio, is the coupling efficiency of the read-out SQUID to the SQD. Difficulty in implementing the array is determined by the process of fabricating the read-out SQUID and the SQD, and the numerous circuit connections which contribute to the complexity of the array.
In light of the foregoing, there is a need for an array of superconductive quantum detectors that has an increased output signal to achieve a better signal-to-noise ratio, and which can be more readily manufactured at a lower cost.